Everybody talks about high-performance camshafts, valvesprings, and roller-rocker systems, but you don't hear much about how to set them up. When it comes to performance engines, the devil is in the details. A performance camshaft won't deliver much if you are always bending pushrods, breaking valvesprings, and generally abusing the valvetrain because it is set up improperly. We're going to show you exactly how to properly set up a valvetrain. There are several key points that you should always check when creating a performance valvetrain. Rather than bore you with paragraph after paragraph of words, we're going to show you how it's done with photos and captions. We'll assume that you've just pickup your heads from the machine shop and it's time to assemble them for that new engine you're building. Do you have enough clearance to coil-bind? Will the retainers hit the seals? The only way to know is to measure all this stuff and we'll show you how it's done.
Even if you never intend to build a set of heads yourself, knowing how it's done can be just as important the next time you run across a valvetrain problem that seems to have everyone stumped. So climb on board our valve training exercise and learn the right way to assemble those valves, springs, and rockers.
High-quality valves are a great place to start building a high-performance head. There has never been a wider selection of stainless steel valves than there are today. Companies like Federal-Mogul, Ferrea, Manley, Milodon, SSI, and many others offer excellent parts at a reasonable price. |
Installed height is the distance between the bottom of the retainer and the spring seat in the head. This Comp Cams illustration also reveals the retainer-to-seal clearance that must be a minimum of 0.050 inch. |
A height mic is a great tool for measuring actual installed height. Read the tool like a micrometer. In this instance, the installed height is 1.875 inch. If the height measures more, you can install shims under the springs to reduce it. This also increases spring pressure throughout the entire lift curve. |
If you plan to do the job correctly, test the springs on a spring-pressure tester to ensure they measure up to their specs. If you're using dual springs, use the actual retainer when measuring both springs at the same time. |
When measuring installed height, always check the exact valve, retainer, and keepers for that particular assembly. The easiest way to do this is to line up all the pieces with the head to keep everything organized. |
Coil-bind is a major concern when using a high-lift cam. The first thing to do is to gently check the spring's actual compressed, coil-bind height in a vise. What you may find is that the spring checks around 0.030- to 0.050-inch shorter than the published spec. If you use the measured spec, you must check every spring and record each compressed height. Minimum coil-bind clearance is 0.060 inch. |
If the installed height is greater than your spec, you can use shims to decrease the overall height. |
For big dual springs, it's best to step up to the new generation of 10-degree retainers and locks (left) that offer a larger locking surface to the retainer. These larger keepers can only be used with matching 10-degree retainers. |
Most heads will require machining the valveguide to mount the seals. A machine shop can do this, or you can purchase the cutters directly from the cam companies. |
The new generation of rubber valveguide seals are far superior to those hard white plastic seals, but be sure to measure the clearance between the seal and the inside diameter of the spring. There should be a minimum of 0.050-inch clearance. |
Assembling a head requires a quality valvespring compressor. Proform and Powerhouse offers this slick over-center spring compressor that can compress even those killer dual springs. |
Once the valves are installed, it's a good idea to bolt the heads on the engine and install the screw-in studs and guideplates to ensure that the guideplates align the rockers with the valves. Often, the rockers won't line up properly. If so, Iskenderian makes adjustable guideplates that can be used. These must be welded together once the proper spread is established. |
When using larger diameter valvesprings, it's a smart move to check the clearance between the rocker arm and the retainer. Often, this clearance can get tight. Interference here on just some rockers can be traced to budget rocker studs that are not straight. We've seen studs with 0.030 inch of runout! |
Roller rockers come in many variations. This is a comparison of a standard roller (left) with a guided or rail rocker (right). Never use rail rockers with guideplates. This may create a bind that could break parts. |